Catheter for uniform delivery of medication

ABSTRACT

The present invention provides a catheter for the delivery of fluid medication across an anatomical region. In accordance with some embodiments, the catheter includes an elongated tubular member made of a porous membrane. The porous membrane is configured so that a fluid introduced into an open end of the tubular member will flow through side walls of the tubular member at a substantially uniform rate along a length of the tubular member. In accordance with other embodiments, the catheter includes an elongated “weeping” tubular coil spring attached to an end of, or enclosed within, a tube. Fluid within the spring and greater than or equal to a threshold pressure advantageously flows radially outward between the spring coils. Advantageously, the fluid is dispensed substantially uniformly throughout a length of the spring. In accordance with other embodiments, the catheter includes a tube having a plurality of exit holes in a side wall of the tube. The exit holes combine to form a flow-restricting orifice of the catheter. Advantageously, fluid within the catheter flows through all of the exit holes, resulting in uniform distribution of fluid within an anatomical region.

RELATED APPLICATIONS

This application is a continuation of copending U.S. patent applicationSer. No. 10/085,169, filed Feb. 25, 2002, which is a divisionalapplication of U.S. patent application Ser. No. 09/363,228, filed Jul.19, 1999, now U.S. Pat. No. 6,350,253, the entire contents of which arehereby expressly incorporated by reference herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention generally relates to catheters and, in particular, to acatheter that delivers fluid medication uniformly across an infusionsection of the catheter.

2. Description of the Related Art

Infusion catheters for delivery of fluid medication into anatomicalsystems, such as the human body, are well known in the art. Suchcatheters generally include a flexible hollow tube inserted into someregion of the anatomy. The tube typically contains one or more axiallumens within which the fluid may flow. The proximal end of the cathetertube is connected to a fluid source from which fluid is introduced intothe catheter tube. The fluid flows within one of the lumens underpressure supplied at the proximal end of the tube. For each lumen, thereare commonly provided one or more exit holes along an infusion sectionnear the distal end of the tube, for fluid to exit the tube. Such exitholes are created by piercing the side wall of the hollow tube.

In certain medical conditions, it is advantageous to deliver fluidmedication to a plurality of sites within a wound area. For instance,some wounds which require pain medication may be in communication withmany nerve endings, rather than a single nerve trunk. One example ofsuch a wound is a surgical incision. As stated above, it is known toprovide a plurality of exit holes through which the fluid medicationexits the catheter tube. The exit holes may be provided at various axialand circumferential positions along the catheter tube in order tocontrol the position of the medication delivery sites. An example of acatheter having this configuration is disclosed in U.S. Pat. No.5,800,407 to Eldor. Also, in some cases it is desirable to deliver suchmedication under low pressure, so that the fluid is delivered at arelatively low rate. For example, some pain medications must bedelivered slowly to avoid toxicity and other side effects. Furthermore,in many cases it is desirable to dispense fluid medication at asubstantially uniform rate throughout the infusion section of thecatheter, so that the medication is evenly distributed throughout thewound area.

Unfortunately, a limitation of prior art catheters with multiple exitholes, such as the catheter taught by Eldor, is that during low pressuredelivery of fluid medication the fluid tends to exit only through theexit hole(s) nearest to the proximal end of the infusion section of thecatheter tube. This is because fluids flowing through a tube morereadily exit through the exit holes offering the least flow resistance.The longer the flow path followed by the fluid in the lumen, the higherthe flow resistance and pressure drop experienced by the fluid. The mostproximal holes offer the least flow resistance and pressure drop.Therefore, the fluid tends to exit the catheter tube primarily throughthese exit holes. As a result, the fluid medication is delivered only toa small region within the wound area. The tendency of the fluid toundesirably flow only through the most proximal exit holes depends uponthe hole size, the total number of exit holes, and the flow rate. As thehole size or number of holes increases, the fluid becomes more likely toexit only through the most proximal holes. Conversely, as the flow rateincreases, the fluid becomes less likely to do so.

The tendency of the fluid to undesirably exit only through the mostproximal holes of the catheter can in some cases be overcome byincreasing the flow rate or pressure of the fluid, which causes thefluid to flow through more of the exit holes of the catheter. Indeed, ifthe flow rate or pressure is sufficiently high, the fluid will flowthrough all of the exit holes. However, sometimes it is medicallydesirable to deliver medication at a relatively slow rate, i.e., at alow pressure. Also, even in those cases in which high pressure fluiddelivery is acceptable or desirable, prior art catheters do not providefor uniform fluid delivery along the infusion section of the catheter.Rather, the flow rate through the exit holes nearer to the proximal endof the infusion section tends to be greater than that through the exitholes nearer to the distal end. This is because the fluid passingthrough the more proximal holes experiences a lower flow resistance andpressure drop. In contrast, the fluid flowing through the more distalholes experiences greater flow resistance and pressure drop, andconsequently exits at a lower flow rate. The further distal the hole,the lower the exit flow rate of the fluid. As a result, there is anuneven distribution of medication throughout the wound area.

In another known type of infusion catheter, several lumens are providedwithin a catheter tube. For each lumen, one exit hole is provided bypiercing a hole within the wall of the tube. The exit holes are providedat different axial positions along the infusion section of the cathetertube. In this manner, fluid medication may be delivered to severalpositions within the wound area. While this configuration offersimproved fluid distribution, it has some disadvantages. One disadvantageis that the fluid flow rates through the exit holes are not equal, sincethe more distal exit holes offer a greater flow resistance for the samereasons discussed above. Another disadvantage is that the number oflumens, and consequently the number of fluid exit holes, is limited bythe small diameter of the catheter tube. As a result, fluid may bedelivered only to a very limited number of positions within the woundarea. Yet another disadvantage is that the proximal ends of the lumensmust be attached to a complicated manifold which increases the cost ofmanufacturing the catheter.

An example of a catheter providing a more uniform dispensation of fluidmedication throughout an infusion section of the catheter is illustratedby U.S. Pat. No. 5,425,723 to Wang. Wang discloses an infusion catheterincluding an outer tube, an inner tube concentrically enclosed withinthe outer tube, and a central lumen within the inner tube. The innertube has a smaller diameter than the outer tube, so that an annularpassageway is formed therebetween. The outer tube has a plurality ofevenly spaced exit holes defining the infusion section of the catheter.In use, fluid flowing within the central lumen passes throughstrategically positioned side holes within the side walls of the innertube. In particular, the spacing between adjacent side holes decreasesalong a length of the inner tube to induce more fluid to pass throughthe more distal side holes. The fluid then flows longitudinally throughthe annular passageway before exiting through the exit holes in theouter tube wall. In the annular passageway, the fluid can flow in adistal or proximal direction, depending on the location of the nearestexit hole in the outer tube. This configuration is provided to induce amore uniform exit flow rate of fluid from the catheter.

Unfortunately, the Wang catheter is only effective for relatively highpressure fluid delivery. When used for relatively low pressure fluiddelivery, the catheter disclosed by Wang does not provide uniformdispensation of fluid. Instead, the fluid tends to exit through the sideholes of the inner and outer tubes that are nearest to the proximal endof the infusion section of the catheter, since these holes offer theleast flow resistance. Even for high pressure fluid delivery, there areseveral limitations of this design. One limitation is that theconcentric tubes design is relatively complex and difficult tomanufacture. Both tubes must be flexible enough to permitmaneuverability through an anatomical system, yet the annular passagewaymust remain open so that fluid may flow uniformly therein. Anotherlimitation is that the annular passageway may be disturbed if there is abend in the infusion section of the tube. A bend in the catheter maydeform the annular passageway or even cause the inner and outer tubes tocome into contact. This can cause an uneven fluid pressure within alongitudinal cross-section of the annular passageway, resulting innon-uniform fluid delivery.

Thus, there is a need for an improved infusion catheter for deliveringfluid medication uniformly along its infusion section in a relativelysimple, easy to manufacture design which is effective for both high flowrate and low flow rate fluid delivery. Furthermore, it is recognizedthat a particular class of catheters, such as the Wang catheter, mayprovide uniform fluid delivery only at high fluid pressure or flowrates. However, there is a need for an infusion catheter belonging tothis class that has a relatively simple, easy to manufacture design andcan maintain uniform fluid delivery while bent or otherwise physicallydeformed.

SUMMARY OF THE INVENTION

Accordingly, it is a principle object and advantage of the presentinvention to overcome some or all of these limitations and to provide animproved catheter for delivering fluid medication to a wound area of ananatomical region.

In accordance with one embodiment the present invention a catheter isprovided for the uniform delivery of fluid across an anatomical region,comprising an elongated tubular member made of a porous membrane. Themembrane is sized to be inserted through a subcutaneous layersurrounding the anatomical region, such as a person's skin. The membraneis configured so that a fluid introduced under pressure into an open endof the tubular member will flow through side walls of the tubular memberat a substantially uniform rate along a length of the tubular member.The present invention also provides a method of uniformly deliveringfluid throughout an anatomical region, comprising the steps of insertingthe elongated tubular member into the anatomical region and introducinga fluid under pressure into an open end of the tubular member.

Another embodiment of the present invention provides a catheter andmethod for the uniform delivery of fluid throughout an anatomicalregion. The catheter comprises an elongated support and a porousmembrane wrapped around the support. The support is configured so thatone or more lumens are formed between the support and the membrane.Alternatively, the support may be a tubular member having a plurality ofholes therein. The method comprises the steps of inserting theabove-described catheter into the anatomical region and introducing afluid under pressure into the proximal end of at least one of thelumens. Advantageously, the fluid passes through the membrane at asubstantially uniform rate into the anatomical region. The presentinvention further provides a method of manufacturing this cathetercomprising the steps of forming an elongated support and wrapping aporous membrane around the support so that one or more lumens are formedbetween the support and the membrane.

Another embodiment of the present invention provides a catheter andmethod for the uniform delivery of fluid throughout an anatomicalregion. The catheter comprises an elongated tube including a pluralityof exit holes along a length thereof and a tubular porous membraneconcentrically enclosed within the tube. The tube and membrane define alumen. The method comprises the steps of inserting the above-mentionedcatheter into the anatomical region and introducing a fluid underpressure into the proximal end of the lumen so that the fluidadvantageously passes through the membrane and the exit holes at asubstantially uniform rate into the anatomical region. The presentinvention further provides a method of manufacturing this catheter,comprising the steps of forming an elongated tube, providing a pluralityof exit holes along a length of the tube, forming a tubular porousmembrane, and concentrically enclosing the tubular porous membranewithin the tube so that the tube and membrane define a lumen.

Yet another embodiment of the present invention provides a device andmethod for the uniform delivery of fluid throughout an anatomicalregion. The device is advantageously simple and easy to manufacture,comprising an elongated catheter having a plurality of exit holes alonga length thereof. The exit holes may serve as the flow-restrictingorifice. Alternatively, a flow-restricting orifice may be providedelsewhere within the catheter or proximal to the catheter. The exitholes may gradually increase in size along the length of the catheter,so that the largest exit hole is further distal than the smallest exithole. Alternatively, the holes can be laser drilled and be ofapproximately the same size. Advantageously, a fluid flowing underpressure within the catheter will flow through substantially all of theexit holes at a substantially equal rate. The method comprises the stepsof inserting the catheter into the anatomical region and introducing afluid under pressure into the proximal end of the catheter. The fluidflows through the exit holes and enters the anatomical region,advantageously flowing through substantially all of the exit holes at asubstantially equal rate. The present invention further provides amethod of manufacturing this device, comprising the steps of forming anelongated catheter and providing a plurality of exit holes along alength of the catheter in a manner so that the exit holes graduallyincrease in size along the length of the catheter from the proximal endto the distal end thereof.

Yet another embodiment of the present invention provides a catheter andmethod for delivering fluid medication to an anatomical region. Thecatheter comprises a tube, a “weeping” tubular coil spring attached to adistal end of the tube, and a stop closing a distal end of the spring.The tube and spring each define a portion of a central lumen. The springhas adjacent coils in contact with one another so that fluid within thespring and below a threshold dispensation pressure is prevented fromexiting the lumen by flowing radially between the coils. The spring hasthe property of stretching when the fluid pressure is greater than orequal to the threshold dispensation pressure permitting the fluid to bedispensed from the lumen by flowing radially between the coils, i.e.“weeping” through the spring. Advantageously, the fluid is dispensedsubstantially uniformly throughout the length and circumference of aportion of the spring. In use, fluid is introduced into an open proximalend of the tube, allowed to flow into the spring, and brought to apressure greater than or equal to the threshold dispensation pressure sothat the fluid weeps through the spring.

Yet another embodiment of the present invention provides a catheter andmethod for delivering fluid medication to an anatomical region. Thecatheter comprises a distally closed tube and a “weeping” tubular coilspring, as described above, concentrically enclosed within the tube. Aplurality of exit holes are provided in side walls along a length of thetube, defining an infusion section of the tube. The spring is enclosedwithin the infusion section so that a lumen is defined within the tubeand spring. In use, fluid is introduced into a proximal end of the tube,allowed to flow into the spring, and brought to a pressure greater thanor equal to the threshold dispensation pressure of the spring so thatthe fluid is dispensed from the lumen by weeping through the spring andthen flowing through the exit holes of the tube.

For purposes of summarizing the invention and the advantages achievedover the prior art, certain objects and advantages of the invention havebeen described herein above. Of course, it is to be understood that notnecessarily all such objects or advantages may be achieved in accordancewith any particular embodiment of the invention. Thus, for example,those skilled in the art will recognize that the invention may beembodied or carried out in a manner that achieves or optimizes oneadvantage or group of advantages as taught herein without necessarilyachieving other objects or advantages as may be taught or suggestedherein.

All of these embodiments are intended to be within the scope of theinvention herein disclosed. These and other embodiments of the presentinvention will become readily apparent to those skilled in the art fromthe following detailed description of the preferred embodiments havingreference to the attached figures, the invention not being limited toany particular preferred embodiment(s) disclosed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic side view of a catheter having features andadvantages in accordance with a first embodiment of the presentinvention;

FIG. 2 is a sectional view of the catheter of FIG. 1, taken along line2-2 of FIG. 1;

FIG. 3 is a sectional view of the catheter of FIG. 1, taken along line3-3 of FIG. 1;

FIG. 4 is a perspective view of the end portion and support beam of thecatheter of FIG. 1, illustrating a cross-section taken along line 4-4 ofFIG. 1;

FIG. 5 is a side view of a catheter having features and advantages inaccordance with a second embodiment of the present invention;

FIG. 6 is a cross-sectional view of the infusion section of the catheterof FIG. 5 taken along line 6-6 of FIG. 5;

FIG. 7 is a cross-sectional view of a catheter having features andadvantages in accordance with a third embodiment of the presentinvention;

FIG. 8 is a side view of a catheter having features and advantages inaccordance with a fourth embodiment of the present invention;

FIG. 9 is a side view of a catheter having features and advantages inaccordance with a fifth embodiment of the present invention;

FIG. 10A is a cross-sectional view of the catheter of FIG. 9,illustrating an unstretched state of the spring;

FIG. 10B is a cross-sectional view of the catheter of FIG. 9,illustrating a stretched state of the spring;

FIG. 11 is a cross-sectional view of a catheter having features andadvantages in accordance with a sixth embodiment of the presentinvention; and

FIG. 12 is a side view of a catheter having features and advantages inaccordance with the sixth embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIGS. 1-4 illustrate an infusion catheter 20 according to one embodimentof the present invention. Catheter 20 preferably includes a flexiblesupport 22 (FIGS. 2-4), a non-porous membrane 24, and a porous membrane26. The membranes 24 and 26 are wrapped around the support 22 to form aplurality of axial lumens between the inner surfaces of the membranes 24and 26 and the surface of the support 22, as described in greater detailbelow. The non-porous membrane 24 defines a non-infusing section 28 ofthe catheter 20, and preferably covers the support 22 from the proximalend thereof to a point 30, shown in FIG. 1. Similarly, the porousmembrane 26 defines an infusion section 32 of catheter 20, andpreferably covers the support 22 from the point 30 to the distal end ofsupport 22. Alternatively, the catheter 20 may be configured without anon-porous membrane 24. In this configuration, the porous membrane 26covers the entire length of the support 22, so that the entire length ofthe support 22 corresponds to the infusion section of the catheter 20.The infusion section can have any desired length. The proximal end ofthe catheter 20 may be connected to a fluid supply 34 containing a fluid36 such as a liquid medication. The distal end of catheter 20 mayinclude a cap 48 (FIG. 4) defining the endpoint of the axial lumenswithin the catheter 20.

In use, the catheter 20 is inserted into an anatomical system, such as ahuman body, to deliver fluid medication directly to a wound area withinthe anatomical system. In particular, the catheter 20 is designed todeliver medication throughout a generally linear segment of the woundarea, corresponding to the infusion section 32 of the catheter 20. Thus,the catheter is preferably inserted so that the infusion section 32 ispositioned within the wound area. By using well known methods, aphysician or nurse may insert the catheter 20 with the aid of an axialguide wire 46 positioned within an axial guide wire lumen 44 of thecatheter. Once the catheter is positioned as desired, the guide wire 46is simply pulled back out through the proximal end of the catheter 20.Alternatively, the catheter 20 may be provided without a guide wire or aguide wire lumen.

FIGS. 2 and 3 illustrate a preferred configuration of the support 22.The surface of the support 22 includes interruptions such as a pluralityof ribs 40 as shown in the figures. The interruptions are configured sothat when the membranes 24 and 26 are wrapped around the support 22, themembranes form a portion of the walls of a plurality of axial lumens 38within which the fluid 36 may flow. In a preferred configuration, aplurality of ribs 40 extend radially from a common axial center portion42 of the support 22. The ribs 40 also extend longitudinally along alength of the support 22, and preferably along the entire lengththereof. In the non-infusing section 28, shown in FIG. 2, the non-porousmembrane 24 is preferably tightly wrapped around the outer edges of theribs 40. As a result, the axial lumens 38 are formed between the innersurface of the non-porous membrane 24 and the outer surface of support22. Similarly, in the infusion section 32, shown in FIG. 3, the porousmembrane 26 is preferably tightly wrapped around the outer edges of theribs 40, so that the axial lumens 38 are formed between the innersurface of porous membrane 26 and the outer surface of support 22.

In an alternative embodiment of the catheter 20, the porous membrane 26may be wrapped around the entire length of the support 20, thusreplacing the non-porous membrane 24. In this embodiment, the entirelength of the support 22 corresponds to the infusion section 32.According to another alternative embodiment, the support 22 may extendonly within the infusion section 32, and a tube may be providedextending from the fluid supply 34 to the proximal end of the support22. In this embodiment, the tube replaces the non-porous membrane 24 andthe portion of the support 22 extending within the non-infusing section28 of the preferred embodiment. In other words, the tube defines thenon-infusing section 28.

In the preferred configuration, the number of ribs 40 equals the numberof axial lumens 38. Although five ribs 40 and axial lumens 38 are shownin FIGS. 2 and 3, any suitable number of ribs 40 and lumens 38 may beprovided, giving due consideration to the goals of providing a pluralityof lumens within the catheter 20, maintaining flexibility, and, ifdesired, maintaining the fluid independence of the lumens. Herein, theterms “fluid independence,” “fluid separation,” and the like, when usedto describe a plurality of axial lumens, simply mean that the lumens donot fluidly communicate with each other. The membranes 24 and 26 arepreferably glued along the outer edges of the ribs 40, utilizing anysuitable glue, such as a medical grade glue or epoxy. This prevents themembranes 24 and 26 from slipping, which might occur as the catheter isinserted or removed from the anatomy. More preferably, the membranes areglued along the entire length of the outer edges of each of the ribs 40.Alternatively, the membrane may be wrapped around the support and notsecured to the support by a foreign substance. The membrane and supportmay also be secured to each other by other means known to those of skillin the art. This maintains the fluid independence of the lumens 38. Ifdesired, an axial guide wire lumen 44 may be provided within the axialcentral portion 42 of the support 22. The guide wire lumen 44 is adaptedto receive a guide wire 46 which may be used to aid in the insertion ofthe catheter 20 into the anatomy, as described above and as will beeasily understood by those of skill in the art.

As shown in FIG. 4, the catheter 20 preferably includes an end portionor cap 48 secured to the distal end of support 22. End portion 48 may beformed integrally with the support 22 or may be adhesively bondedthereto. Preferably, the proximal end of end portion 48 is circular andhas a diameter such that the outer surface of the proximal end of endportion 48 is aligned with the outer edges of the ribs 40 of the support22, as shown. The porous membrane 26 is wrapped around the proximal endof the end portion 48. The membrane 26 is preferably glued to the endportion 48 so that fluid 36 within the lumens 38 is prevented fromexiting the catheter 20 without passing through the walls of themembrane 26. End portion 48 blocks axial fluid flow through the distalend of catheter 20. However, end portion 48 may optionally be formedfrom a porous material to permit some axial dispensation of fluid fromthe distal end of the catheter 20, if desired. The distal end of endportion 48 is preferably dome-shaped, as shown, to permit the catheter20 to more easily be inserted into an anatomical region.

The support 22 can be formed from a variety of materials, giving dueconsideration to the goals of flexibility, light-weight, strength,smoothness, and non-reactivity to anatomical systems, i.e., safety.Suitable materials for the support 22 include nylon, polyamide, teflon,and other materials known to those skilled in the art. The porousmembrane 26 is preferably a sponge-like or foam-like material or ahollow fiber. The membrane 26 may be formed from a variety of suitablematerials, giving due consideration to the goals of being flexible andnon-reactive to anatomical systems. The membrane 26 preferably has aporosity resulting in substantially uniform dispensation of fluid alongthe surface area of the infusion section 32 of the catheter 20, and hasan average pore size sufficiently small to limit the flow of bacteriathrough the membrane walls. Some suitable materials for the membrane 26are polyethylene, polysulfone, polyethersulfone, polypropylene,polyvinylidene difluoride, polycarbonate, nylon, or high densitypolyethylene. These materials are advantageously biocompatible. Theporous membrane 26 may filter out unwanted bacteria from the fluidmedication as it passes through the membrane 26. It is known that thesmallest bacteria cannot pass through a pore any smaller than 0.23microns. Thus, the average pore size, or pore diameter, of the porousmembrane 26 may be less than 0.23 microns to prevent bacteria fromtraversing the membrane 26. The average pore size, or pore diameter, ofthe membrane 26 is preferably within the range of about 0.1 to 1.2microns, more preferably within the range of about 0.3 to 1 micron, andeven more preferably about 0.8 microns.

As mentioned above, the proximal end of catheter 20 may be connected toa fluid supply 34. The catheter 20 may be configured so that each axiallumen 38 is fluidly independent. In other words, the lumens 38 would notfluidly communicate with one another. The catheter 20 may be connectedto a single fluid supply 34, so that the fluid 36 flows within each ofthe lumens 38. Alternatively, the catheter 20 may be connected to aplurality of separate fluid supplies so that several different fluidsmay separately flow within the lumens 38. According to thisconfiguration, each lumen 38 may be connected to a separate fluid supplyso that the total number of different fluids that may be delivered tothe anatomy is equal to the number of lumens 38. Alternatively, thefluid lumens need not be fluidly independent. For example, the membrane26 may not be secured to the support 22 along the entire length of thesupport 22, thus permitting fluid 36 to migrate between lumens 38.

In operation, the catheter 20 delivers fluid directly to the area of theanatomy that is adjacent to the infusion section 32. The fluid 36 fromthe fluid source 34 is introduced into the axial lumens 38 at theproximal end of the catheter 20. The fluid 36 initially flows throughthe non-infusing section 28. When the fluid 36 first reaches theinfusion section 32, it soaks into the porous membrane 26. As more fluid36 enters the infusion section 32, it diffuses longitudinally within thewalls of the membrane 26 until the entire membrane 26 and infusionsection 32 are saturated with fluid. At this point the fluid 36 beginsto pass through the membrane 26, thereby exiting the catheter 20 andentering the anatomy. Moreover, the fluid 36 advantageously passesthrough the entire surface area of the porous membrane 26 at asubstantially uniform rate, due to the characteristics of the membrane26. Thus, the fluid is delivered at a substantially equal ratethroughout a generally linear segment of the wound area of the anatomy.Furthermore, this advantage is obtained for both low and high pressurefluid delivery.

FIGS. 5 and 6 illustrate a catheter 50 according to an alternativeembodiment of the present invention. According to this embodiment, thecatheter 50 includes an elongated outer tube 52 and an inner elongatedtubular porous membrane 54. The tubular membrane 54 is preferablyconcentrically enclosed within the outer tube 52. More preferably, thetube 52 tightly surrounds and supports the tubular membrane 54 so that arelatively tight fit is achieved between the inner dimensions of tube 52and the outer dimensions of membrane 54. A plurality of fluid exit holes56 are provided within the tube 52, preferably throughout the entirecircumference thereof. The portion of tube 52 that includes the exitholes 56 defines the infusion section of catheter 50. The tubularmembrane 54 need only be provided along the length of the infusionsection, but could be longer. Optionally, axial exit holes may beprovided within the distal tip 58 of the tube 52. Also, a guide wireand/or guide wire lumen may be provided to aid in the insertion of thecatheter 50 into the anatomy, as will be understood by those skilled inthe art.

The tube 52 may be formed from any of a variety of suitable materials,such as nylon, polyimide, teflon and other materials known to thoseskilled in the art, giving due consideration to the goals ofnon-reactivity to anatomical systems, flexibility, light-weight,strength, smoothness, and safety. In a preferred configuration, the tube52 is preferably a 20 gauge catheter tube, having inside and outsidediameters of 0.019 inches and 0.031 inches, respectively. The exit holes56 of tube 52 are preferably about 0.015 inches in diameter and providedat equally spaced axial positions along the tube 52. The holes 56 arepreferably arranged so that every hole is angularly displaced about 120°relative to the longitudinal axis of the tube 52, from the angularlocation of the previous hole. The axial separation between adjacentexit holes 56 is preferably within the range of about 0.125 to 0.25inches, and more preferably about 3/16 inch. Also, the infusion sectioncan have any desirable length. This configuration results in a thorough,uniform delivery of fluid throughout a generally linear segment of thewound area. Of course, the exit holes 56 may be provided in any of avariety of alternative arrangements.

The tubular porous membrane 54 is preferably a sponge-like or foam-likematerial or a hollow fiber. The tubular membrane 54 may have an averagepore size, or pore diameter, less than 0.23 microns to filter bacteria.The pore diameter is preferably within the range of about 0.1 to 1.2microns, more preferably within the range of about 0.3 to 1 micron, andeven more preferably about 0.8 microns. The tubular membrane 54 may beformed from any of a variety of suitable materials, giving dueconsideration to the goals of non-reactivity to anatomical systems,maintaining flexibility, fitting within the size constraints of the tube52, and having a porosity resulting in the substantially uniformdispensation of fluid through all of the exit holes 56 in tube 52. Somesuitable materials for the membrane 54 are polyethylene, polysulfone,polyethersulfone, polypropylene, polyvinylidene difluoride,polycarbonate, nylon, or high density polyethylene. Preferable insideand outside diameters of the tubular membrane 54 are 0.010 inches and0.018 inches, respectively. In the event that a guide wire 46 isprovided, the guide wire may be a stainless steel wire about 0.005inches in diameter. The tube 52 may be secured to the membrane 54 byepoxy or other means known to those skilled in the art. Alternatively,the membrane 54 may contact the tube 52 with an interference fit and notuse other materials to secure the membrane 54 in the tube 52.

In operation, the catheter 50 delivers fluid to the region of ananatomical system adjacent to the infusion section of catheter 50. Asthe fluid flows into the infusion section, it initially soaks into thetubular porous membrane 54. As more fluid enters the infusion section,the fluid diffuses longitudinally within the walls of the tubular member54. Once the membrane 54 and the tubular space therein are saturated,the fluid passes through the membrane 54 and exits the catheter 50 byflowing through the exit holes 56 of the tube 52. Moreover, the fluidadvantageously passes through the membrane substantially uniformlythroughout the surface area of the membrane 54, resulting in asubstantially uniform flow through substantially all of the exit holes56. Thus, the fluid is delivered at a substantially equal ratethroughout the wound area of the anatomy. Furthermore, this advantage isobtained for both low and high pressure fluid delivery.

FIG. 7 illustrates a catheter 70 according to another embodiment of thepresent invention. Catheter 70 includes a tube 72 having a plurality ofexit holes 76 in side walls of the tube, and a tubular porous membrane74 concentrically enclosing the tube 72. Catheter 70 operates in asimilar manner to catheter 50 described above in connection with FIGS. 5and 6. In use, fluid medication passes through the exit holes 76 andthen begins to soak into the porous membrane 74. The fluid diffuseslongitudinally within the walls of the membrane until the membrane issaturated. Thereafter, the fluid leaves the membrane walls and entersthe anatomy. Advantageously, the fluid is dispensed to the anatomy at asubstantially uniform rate throughout the surface area of the membrane74. As in the previous embodiments, this advantage is obtained for bothlow and high pressure fluid delivery.

FIG. 8 illustrates a catheter 60 according to another embodiment of thepresent invention. Catheter 60 is better suited for relatively high flowrate delivery of fluid to a region within an anatomical system. Catheter60 includes a tube 62 having a plurality of exit holes 64 of increasingsize. In particular, the more distal exit holes are larger in diameterthan the more proximal exit holes. The position of the exit holes 64 onthe tube 62 defines the length of the infusion section of the catheter60. The infusion section can have any desired length. The proximal endof catheter 60 is connected to a fluid supply, and a guide wire and/orguide wire lumen may also be provided for aiding in the insertion ofcatheter 60 into the anatomy.

As discussed above, for high or low pressure fluid delivery, exit holesnearer to the distal end of a catheter tube generally have increasedflow resistance compared to exit holes nearer to the proximal end of thetube. Also, the fluid flowing through the more distal holes experiencesa greater pressure drop. Consequently, there is generally a greater flowrate of fluid through the more proximal holes, resulting in non-uniformfluid delivery. In contrast, catheter 60 advantageously providessubstantially uniform fluid delivery through substantially all of theexit holes 64, under relatively high flow rate conditions. This isbecause the larger size of the more distal holes compensates for theirincreased flow resistance and pressure drop. In other words, since themore distal holes are larger than the more proximal holes, there is agreater flow rate through the more distal holes than there would be ifthey were the same size as the more proximal holes. Advantageously, theholes 64 are provided in a gradually increasing size which results insubstantially uniform fluid delivery. In addition, the exit holes 64 maybe sized so that they combine to form a flow-restricting orifice, asdescribed below in connection with the embodiment of FIG. 12.

As compared to prior art catheters, catheter 60 is advantageously simpleand easy to manufacture. All that is required is to drill a plurality ofexit holes 64 in the tube 62. Furthermore, catheter 60 can sustaingreater bending than prior art catheters while maintaining operability.In contrast to prior art catheters, such as the Wang catheter, if thetube 62 is bent somewhat, it will still deliver fluid relativelyuniformly. This is because the tube 62 has a single lumen with arelatively large cross-section. When the tube 62 is somewhat bent, fluidflowing within the lumen is less likely to experience blockage and aconsequent pressure change which might lead to non-uniform fluiddispensation.

The tube 62 of catheter 60 may be formed from any of a wide variety ofmaterials, giving due consideration to the goals of non-reactivity toanatomical systems, flexibility, light-weight, strength, smoothness, andsafety. Suitable materials include nylon, polyimide, teflon, and othermaterials known to those skilled in the art. The infusion section canhave any desired length but is preferably about 0.5 to 20 inches long,and more preferably about 10 inches long. The diameter of the exit holes64 preferably ranges from about 0.0002 inches at the proximal end of theinfusion section to about 0.01 inches at the distal end thereof. Thelargest, i.e., most distal, exit hole 64 is preferably about 0.25 inchesfrom the distal end of the tube 62. In the preferred configuration, theaxial separation between adjacent holes 64 is within the range of about0.125 to 0.25 inches, and more preferably about 3/16 inch. Optionally,the holes 64 may be provided so that adjacent holes are angularlydisplaced by about 120° as in the embodiment of FIG. 5. Of course, iftoo many exit holes 64 are provided, the tube 62 may be undesirablyweakened.

FIGS. 9, 10A, and 10B illustrate a catheter 80 according to anotherembodiment of the present invention. The catheter 80 comprises a tube82, a “weeping” tubular coil spring 84, and a stop 86. The proximal endof the spring 84 is attached to the distal end of the tube 82 so thatthe tube and spring each define a portion of a central lumen. Apreferably dome-shaped stop 86 is attached to and closes the distal endof the spring 84. The portion of the spring 84 that is distal to thetube 82 comprises the infusion section of the catheter 80. In anunstretched state, shown in FIG. 10A, the spring 84 has adjacent coilsin contact with one another so that fluid within the spring and below athreshold dispensation pressure is prevented from exiting the lumen byflowing radially between the coils. The spring 84 has the property ofstretching longitudinally, as shown in FIG. 10B, when the fluid pressureis greater than or equal to the threshold dispensation pressure of thespring, thereby permitting the fluid to be dispensed from the lumen by“weeping,” i.e., leaking radially outward between the coils.Alternatively, the spring may stretch radially without elongating topermit fluid to weep through the coils of the spring. Further, thespring may stretch both longitudinally and radially to permit weeping,as will be understood by those of skill in the art. Advantageously, thefluid between the coils of the spring is dispensed substantiallyuniformly throughout the length and circumference of the portion of thespring that is distal to the tube 82, i.e., the infusion section. Thecatheter 80 can be used for both high or low flow rate fluid delivery.

In use, the catheter 80 is inserted into an anatomical region so thatthe spring 84 is in a region to which fluid medication is desired to bedelivered. The spring is initially in an unstretched state, as shown inFIG. 10A. The fluid is introduced into a proximal end of the tube 82 ofthe catheter 80 and flows into and through the spring 84 until itreaches the stop 86. As fluid is continually introduced into theproximal end of the tube 82, the fluid builds inside of the spring 84.When the spring 84 is filled with fluid, the fluid pressure rises morequickly. The fluid imparts a force directed radially outward onto thespring coils. As the pressure builds, the outward force becomes larger.Once the fluid pressure rises to the threshold dispensation pressure,the outward force causes the spring coils to separate slightly so thatthe spring stretches longitudinally, as shown in FIG. 10B.Alternatively, the coils may separate radially, as discussed above. Thefluid then flows through the separated coils to be dispensed from thecatheter 80. Moreover, the dispensation is advantageously uniformthroughout the infusion section of the catheter 80. As fluid iscontinually introduced into the tube 82, the spring 84 remains stretchedto continually dispense fluid to the desired region within the anatomy.If the fluid introduction temporarily ceases, the fluid pressure withinthe spring 84 may fall below the threshold dispensation pressure. If so,the spring will compress so that the coils are once again adjacent andthe fluid is no longer dispensed.

Several spring types will achieve the purposes of this invention.Suitable spring types are 316L or 402L, which can be readily purchased.In a preferred configuration, the spring 84 has about 200 coils per inchalong its length. In this configuration, the spring can advantageouslysustain a high degree of bending without leaking fluid from within, andonly a severe bend will cause adjacent coils to separate. Thus, thespring 84 may be flexed considerably within an anatomical region withoutcausing fluid to leak and therefore be dispensed to only one regionwithin the anatomy. The spring 84 can have any desired length to definethe length of the infusion section of the catheter 80. The spring may beformed from a variety of materials, giving due consideration to thegoals of strength, flexibility, and safety. A preferred material isstainless steel. In the preferred configuration, the inside and outsidediameters of the spring are about 0.02 inches and 0.03 inches,respectively, and the spring wire has a diameter of about 0.005 inches.The proximal end of the spring 84 is preferably concentrically enclosedwithin the distal end of the tube 82. The spring can be glued to theinside wall of the tube 82 using, for example, a U.V. adhesive, apotting material, or other bonding materials. Alternatively, the springcan be soldered within the tube 82 or be fitted with a proximal plug andtightly plugged into the tube 82.

The tube 82 and stop 86 can be formed from any of a variety ofmaterials, giving due consideration to the goals of flexibility,light-weight, strength, smoothness, and safety. Suitable materialsinclude nylon, polyimide, teflon, and other materials known to thoseskilled in the art.

FIG. 11 illustrates a catheter 90 according to another embodiment of thepresent invention. The catheter 90 comprises a distally closed tube 92and a “weeping” tubular coil spring 94 concentrically enclosed withinthe tube 92 so that a lumen is defined within the tube and spring. Aplurality of exit holes 96 are provided along a length of the tube 92,in the side wall thereof. The length of the tube 92 including such exitholes 96 defines an infusion section of the catheter 90. The exit holes96 are preferably provided throughout the walls of the infusion section.The infusion section can have any desired length. In the preferredconfiguration, the axial spacing between adjacent holes 96 is within therange of about 0.125 to 0.25 inches, and more preferably about 3/16inch. Adjacent holes 96 are preferably angularly spaced apart by about120°. The spring 94 is preferably enclosed within the infusion sectionof the catheter and configured similarly to the spring 84 of theembodiment of FIGS. 9, 10A and 10B. The spring 94 is preferably longerthan the infusion portion and positioned so that all of the exit holes96 are adjacent to the spring 94. In this configuration, the fluid isprevented from exiting the lumen without flowing between the springcoils. A stop is preferably attached to the tube to close the distal endthereof. Alternatively, the tube 92 may be formed with a closed distalend. The catheter 90 can be used for high or low flow rate fluiddelivery.

In use, the catheter 90 is inserted into an anatomical region so thatthe infusion section is in a region to which fluid medication is desiredto be delivered. The fluid is introduced into a proximal end of the tube92 of the catheter 90 and flows through the spring 94 until it reachesthe closed distal end of the tube 92. As fluid is continually introducedinto the proximal end of the tube 92, the fluid builds inside of thespring 94. Eventually, the spring 94 becomes filled with fluid, thefluid pressure rises, and the fluid weeps through the spring coils asdescribed above in connection with the embodiment of FIGS. 9, 10A, and10B. Moreover, the fluid flows through the spring coils substantiallyuniformly throughout the length and circumference of the spring 94. Thefluid then exits the tube 92 by flowing through the exit holes 96 of theinfusion section. The exit holes are preferably equal in size so thatthe fluid flows at a substantially equal rate through the exit holes,advantageously resulting in a generally uniform distribution of fluidthroughout a desired region of the anatomy. As fluid is continuallyintroduced into the catheter 90, the spring 94 remains stretched tocontinually dispense fluid from the catheter. If the fluid introductionceases temporarily, the fluid pressure within the spring 94 may fallbelow the threshold dispensation pressure. If so, the spring maycompress so that the coils are once again adjacent and the fluid is nolonger dispensed.

In the preferred configuration, the spring 94 and tube 92 are in contactalong the entire length of the spring, so that the fluid weeping throughthe spring is forced to flow through the holes 96 of the infusionsection. Preferably, one end of the spring 94 is attached to the insidewalls of the tube 92, permitting the other end of the spring to bedisplaced as the spring stretches. The spring can be glued to the tube92 with, for example, a U.V. adhesive, potting material, or otherbonding materials. Alternatively, an end of the spring can be solderedonto the inner walls of the tube 92. The tube 92 can be formed from anysuitable material. The inside walls of the tube 92 are preferably smoothso that the spring can more freely stretch and compress.

FIG. 12 illustrates a catheter 100 according to another embodiment ofthe present invention. The catheter 100 comprises a distally closed tube102 having a plurality of exit holes 104 in side walls of the tube 102.The portion of the tube 102 having exit holes 104 defines an infusionsection of the catheter 100. The exit holes 104 are sized to have acombined area of opening that is smaller than the area of any otherflow-restricting cross-section or orifice of the catheter. Thus, theexit holes 104 are the flow-restrictor of the catheter 100. In use, thecatheter advantageously dispenses fluid through substantially all of theexit holes 104. A fluid introduced into a proximal end of the tube 102flows through the tube until it reaches the closed distal end thereof.At this point, the fluid builds within the infusion portion of thecatheter. The fluid is substantially prevented from flowing through theholes 104, due to their small size. Eventually, the infusion portion ofthe catheter becomes filled with fluid. As fluid is continuallyintroduced into the proximal end of the tube 102, the fluid pressurebegins to build. At some point the pressure becomes sufficiently high toforce the fluid through the exit holes 104. Moreover, the fluid flowsthrough substantially all of the exit holes 104.

In this preferred configuration, the exit holes 104 are all equal insize so that the fluid is dispensed at a substantially equal ratethrough substantially all of the holes. The holes 104 are preferablylaser drilled to achieve a very small hole diameter. A preferreddiameter of the exit holes 104 is about 0.0002 inches, or about 5microns.

Numerous exit holes 104 may be provided within the tube 102. The holesare advantageously provided throughout the circumference of the infusionportion of the catheter 100, to more uniformly deliver the fluidthroughout an anatomical region. A preferred axial spacing betweenadjacent holes 104 is within the range of about 0.125 to 0.25 inches,and more preferably about 3/16 inch. The catheter 100 can be used forhigh or low flow rate fluid delivery. The tube 102 can be formed fromany of a variety of materials known to those skilled in the art anddiscussed previously.

With regard to all of the above embodiments, an independent guide wirelumen may be provided within or adjacent to the lumen(s) disclosed, aswill be understood by those skilled in the art.

Although this invention has been disclosed in the context of certainpreferred embodiments and examples, it will be understood by thoseskilled in the art that the present invention extends beyond thespecifically disclosed embodiments to other alternative embodimentsand/or uses of the invention and obvious modifications and equivalentsthereof. Thus, it is intended that the scope of the present inventionherein disclosed should not be limited by the particular disclosedembodiments described above, but should be determined only by a fairreading of the claims that follow.

1. A method of manufacturing a catheter, comprising: providing adistally closed tube, said tube having a substantially consistentcross-sectional size between a proximal end and a distal end; creating aplurality of exit holes along a distal portion of said tube, saidplurality of exit holes defining an infusion section of said catheter,said plurality of exit holes being spaced in a substantially uniformconfiguration along a length of said infusion section wherein the holesare axially displaced with respect to one another such that no two holesare positioned across from one another with respect to their placementon the tube; positioning an elongated, tubular member within an interiorspace of said tube, said tubular member being sized so that said tubularmember extends the entire length of said infusion section, said tubularmember being formed of a porous material and defining a radiallyinnermost surface of a lumen of said catheter within said infusionsection such that a fluid introduced into a proximal end of said tubewill flow to said infusion section and first contact said tubularmember, saturate said tubular member and then exit said tubular memberprior to being dispensed from said catheter by flowing through said exitholes; and configuring said tube and said tubular member so that saidtube tightly surrounds and maintains contact with said tubular memberalong at least the length of said infusion section.
 2. The catheter ofclaim 1, wherein said plurality of exit holes comprises at least a firstexit hole at a first axial location and at least a second exit hole at asecond axial location of said tubular body.
 3. The catheter of claim 2,wherein a distance between said at least a first exit hole and said atleast a second exit hole is between about 0.125 and 0.25 inches.
 4. Themethod of claim 1, wherein said positioning of said tubular membercomprises positioning said tubular member coaxially within said tube. 5.The method of claim 1, further comprising the step of configuring saidlumen so that a fluid flowing within said lumen will pass through thewalls of said tubular member and exit said tube by flowing throughsubstantially all of said exit holes at a substantially equal rate. 6.The method of claim 1, further comprising the step of configuring saidtube and tubular member to be substantially flexible.
 7. The method ofclaim 1, wherein said exit holes are provided throughout thecircumference of said tube.
 8. The method of claim 1, wherein saidtubular member has an average pore diameter less than 0.23 microns. 9.The catheter of claim 1, wherein the diameter of each of said pluralityof exit holes is substantially equal.
 10. The catheter of claim 1,wherein the plurality of exit holes are positioned along the distalportion of the tube such that adjacent exit holes are angularlydisplaced about 120 degrees from one another.
 11. A method ofmanufacturing a catheter, comprising: providing a distally closed tube,said tube having a substantially consistent cross-sectional size betweena proximal end and a distal end; creating a plurality of exit holesalong a distal portion of said tube, said plurality of exit holesdefining an infusion section of said catheter, said plurality of exitholes being spaced in a substantially uniform configuration along alength of said infusion section, said exit holes angularly displacedwith respect to one another such that no two exit holes are positioneddirectly across from one another with respect to their placement on thetube; positioning an elongated, tubular member within an interior spaceof said tube, said tubular member being sized so that said tubularmember extends the entire length of said infusion section, said tubularmember being formed of a porous material and defining a radiallyinnermost surface of a lumen of said catheter within said infusionsection such that a fluid introduced into a proximal end of said tubewill flow to said infusion section and first contact said tubularmember, saturate said tubular member and then exit said tubular memberprior to being dispensed from said catheter by flowing through said exitholes; and configuring said tube and said tubular member so that saidtube tightly surrounds and maintains contact with said tubular memberalong at least the length of said infusion section.